Héctor Benítez-Pérez

Reconfigurable fault tolerant PID networked control for magnetic levitation case study

Abstract Nowadays dynamic behaviour performed by a computer network system shows the needs to address it from the perspective of a control system. One strategy to be followed it is the real-time modeling. Having obtained a way to represent a computer network system, next stage is to how control approach can be affected and modified. In that respect, this paper proposes a control reconfiguration strategy from the definition of an automata considering computer network reconfiguration. Several stages are studied, how computer network takes place as well as how control techniques is modified.

Application of a Time-Scale Local Hurst Exponent analysis to time series

We present a method for estimating a time-scale local Hurst exponent on time series.The method has proven to be sensitive to sudden behavior changes on time series.Lower scales evaluate short-range correlations.Larger scales evaluate long-range correlations.The analysis evaluates pattern changes regardless the amplitude and scale. This paper introduces a method to perform a Time-Scale Local Hurst Exponent (TS-LHE) analysis for time series. The traditional Hurst exponent methods usually analyze time series as a whole, providing a single value that characterizes their global behavior. In contrast, the methods based on the Local Hurst Exponent allow the evaluation of the fractal structure of a time series on local events. However, a critical parameter in these methods is the selection of scale. Here, a TS-LHE method is presented, based on a systematic implementation of the rescaled-range (R/S) method, in a set of sliding windows of different sizes. This method allows calculating instantaneous values of Local Hurst Exponents at different scales, associating them with individual samples of a time series. This paper is organized as follows: first, an overview of the TS-LHE is provided; then, a proof-of-concept of this analysis is presented, considering (a) different fractional Brownian motion series, (b) a synthetic seismic signal under different noise conditions, and (c) a group of real seismic traces. Finally, the obtained results show that the TS-LHE analysis is particularly sensitive to sudden behavior changes of the time series, such as frequency or phase variations. This sensitivity is independent of the amplitude of the data, and thus, it can be used to identify pattern changes as well as long- and short-range correlations within a time series.

Fuzzy control with estimated variable sampling period for non-linear networked control systems: 2-DOF helicopter as case study

This paper presents a fuzzy controller for class of non-linear networked control systems; the varying time delays and packet loss are taken as a variable sampling period of the system. The variable sampling period is estimated using a time stamped and probability density function. A fuzzy model smoothly switches to estimate the system state; the antecedent input is the estimated sampling period and the consequent part is formed by linear models discretized with specific sampling periods. The fuzzy controller generates a control input using the estimated states to ensure system stability for a wide range of sampling periods. A two-degree-of-freedom helicopter is used to show the applicability and effectiveness of the controller with robustness to traffic.

Bounded communication between nodes of a networked control system as a strategy of scheduling

In a networked control system, several nodes exchange information through a network, to achieve specific control goals and thus increasing network traffic. This affects the overall system performance. Several approaches try to satisfy requirements of both control and communication performance. Particularly, some methodologies have been proposed to save bandwidth. One of such methodologies has been scheduling, which has been studied in depth through the last decade. Commonly, the objective of using scheduling to save bandwidth is to accurately use the computing resources. This paper shows two scheduling strategies, one performing static scheduling and the other carrying out dynamic scheduling, in order to expose the advantages of using dynamic scheduling in an ad hoc implementation. Both strategies execute on a real-time distributed system, and both are able to modify the frequency of transmission as well as the periods of tasks in individual components. Hence, both of them tend to impact on the quality of performance of the system, due to network use. The first scheduling strategy modifies the periods of task, and network access is assigned through a static scheduling algorithm. On the other hand, the second strategy, schedulability, is dynamically achieved by controlling the rate of frequency transmission into a frequency region, bounded by minimum and maximum transmission rates. Numerical simulations are used as implementations of both strategies.

Reconfiguration control strategy using Takagi–Sugeno model predictive control for network control systems – a magnetic levitation case study

Abstract This paper presents a reconfiguration control strategy for network control systems that makes use of a fuzzy Takagi–Sugeno model for predictive control. The dynamic behaviour of a network control system is modelled by using a real-time implementation of the scheduling algorithm. Here, this is applied for a magnetic levitation system, as a plant that is also modelled using a fuzzy Takagi–Sugeno approach. Thus, this paper covers several design issues, such as how to model a computer network, a plant, and a reconfiguration control strategy, as well as how the reconfiguration control strategy is modified using the fuzzy approach.

Reconfigurable Fuzzy Takagi Sugeno Networked Control using EDF Scheduling in xPC Target

Nowadays dynamic behaviour performed by a computer network system shows the posibility to be addressed from the perspective of a control system. This paper discusses the use of Fuzzy Takagi Sugeno real time digital control with hardware-in-the-loop (HIL) magnetic levitator (maglev) using xPC Target. Here xPC Target is used as operating environment for real time processing and to connect a computer network system. In that respect, this paper proposes a control reconfiguration strategy from the definition of a Takagi-Sugeno approach, considering computer network reconfiguration. Several stages are studied, how computer network takes place as well as how control techniques are modified using Fuzzy Takagi- Sugeno Control.

Fault classification SOM and PCA for inertial sensor drift

FDI is an active research field in several areas. In fact, there are still many challenges in on-line detection and identification. Several approaches have been pursued such as model-based or knowledge-based techniques, however, these present several drawbacks like time consumption or the lack of adaptability. Here a proposal to classify faults for both known and unknown scenarios is presented. This is based upon a statistical approach, principal component analysis (PCA), and non-supervised neural networks such as self organizing maps (SOM). Experimental results are presented based upon an aircraft flight dynamics model.

Reconfigurable Fuzzy Takagi Sugeno Networked Control using Cooperative Agents and Local Fault Diagnosis

Nowadays dynamic behaviour performed by a computer network system shows the posibility to be addressed from the perspective of a control system. This paper discusses the use of Fuzzy Takagi Sugeno real time control and local fault diagnosis with hardware-in-the-loop (HIL) magnetic levitator (maglev) using xPC Target. Here xPC Target is used as operating environment for real time processing and to connect a computer network system. In that respect, this paper proposes a control reconfiguration approach based upon a cooperative agent strategy and local fault diagnosis using Takagi-Sugeno technique. Several stages are studied, how local fault diagnosis produce a warning value, how computer network is reconfigured, as well as how control techniques are modified using Fuzzy Takagi-Sugeno Control.

A consensus routing algorithm for mobile distributed systems

This paper introduces a consensus routing algorithm based on an availability function. Such a function obtains a consensus among a group of nodes by evaluating the idle time in the scheduler of each node, along with the general conditions of the network and determining the next step of the route. In this regard, the algorithm proposed here makes it possible to avoid flooding while reducing bandwidth use and keeping changes of the network only at a local scale.

Codesign strategy based upon fuzzy control for networked control systems and a scheduling algorithm

This work presents a supervisory control strategy for Networked Control Systems (NCSs). This shows the identification and control of the plant using fuzzy theory. The fuzzy model incorporates the delay dynamics within the fuzzy rules based upon a real-time scheduling strategy. The controller is composed by a nominal control (PID) and a supervisory control which is proposed from the delay dynamics following the related predefined time delays. A scheduling algorithm is used based upon codesign strategy following mutual correlation among control and network algorithms. A system of magnetic levitation is presented as a case study.